Hello, I'm new to the Bimota Forum although I'm not new to Bimota. I had a Yb4ie a few years ago which I sold to NZ some years after. I bought an SB2 in parts waiting to be restored but couldn't resist a YB9SRI I saw advertised on Dutch marktplaats.nl. The guy accepted my lowish offer and granted me his ride. the bike is in fine fettle. No accident damage but a few mechanical things I would like to have your opinion about.
The fuel filler is missing the pull and turn flap. is this common (that they break) and are there spares availabe? There is no pillion seatover below the seatcover. Last but not least, the owner before the last owner ditched the injection system for a set of Keihin FRC33 flatside carbs. He lost the filterbox but fittted ramair filtersocks over the nice blue plastic bell mouths.
the bike rides nice and strong but idle is initially high but drops after a few minutes of idling after which the bike stalls if you don't save it. Sounds like a rich mixture. Cold starting there is no need for a choke (it doesn't have one, just an idle adjustment screw) Is this a racing carb 'feature' to get used to or can it be adjusted out?
I notice the rev counter overreads with 7000 rpm at slightly over 60mph. and the temp gauge pointer starts behaving like a windscreenwiper when the revs go up.
Cheers,
William

The Thundercat engine has a couple of things that need to be right. First would be the valves tollerances, that might be hard to get at in the Bimota frame. The second is the carbs need to be clean and balanced.
I think Bimota used a different cdi, I don't know if that will work well with carbs._________________Don't read everything you believe

OH , flatsides on a YB9SRi !!!! thats the way to go , the injection was not great , and don't think that had a choke either.
Have flatsides on a few bikes, they can be a pain to start but once bike warm they should run and idle fine . The difference from normal carbs to flatsides is amazing .
Sounds like the YB9 was a good buy Invest in a good setup and it will be amazing !!

Hi Fulvia, and welcome to the Forum....Flatslides...Hhmm...nice.....Have you found a cable on the flatslides with a large knurled black plastic adjuster?

Normally when they got up to temperature the rev range goes higher on idle and you can turn it down with the adjuster....or use the adjuster to turn them up when cold...I've not heard of it happening the other way.....Try adjusting the throttle cable also...maybe theres too much slack in it...that's a quick fix...thread out the adjuster to tighten the throttle cable....Old fuel??? If its starting fine and running fine then run and ride and see if the problems iron out...and put high grade 97 or higher fuel in......Electrics...maybe its not been run for a while...having "juice" running thru the system may clear issues...so ride and use and see if things get better.....Fuel filler cap.....I think Paolo of BimotaClassicParts may have spares....perhaps it was the pin holding the flap that fell out some time ago and the flap went AWOL...the flap is needed to Twist the cap open, and lock the cap with the key......Same filler cap...I think...was used on Bimota SB6 and Db1 and some others....Check BCP for rear seat also....

There is a treaded adjuster but I feel it is not used for turning up and down every time you go out for a ride. Adding to the problem, the rev counter is overexaggerating quite a lot. Idling sounds like slightly below 1500 but it shows 2500. and 7000 in 6th shows 100kph. I wll have to check with a timing lamp. I'm not sure if this is 'normal' for these CEV clocks or if this revcounter can be callibrated inside somewere.
Throttle cable is Ok and the bike runs great altough compaired to my 1000cc Ducati Sport classic it feels more 400 than 600. Luckilly it steers like a 400 too!
I wil check with Paolo if he can help me getting a twist and pull fuel flap.
Is it normal for this bike that you have to fumble quite a lot to install the cap? It seems the tank cover is not perfectly in line with the fueltank opening itself and when I fill her up completely and rest her on the jiffy with filler installed it leaks.
Cheers,
William
PS is it normal for this bike that you can't have the engine running when it is on the jiffy? Even with the clutch lever pulled it doesn't start or run.

I assume this is your first time with flatslides...if there is a knurled adjuster on a wired plastic insulated flexible casing.....that's what its there for....you can tweak it when its running hot to turn down...or turn up when cold to act like a choke...only takes 1/4 to 1/2 turn to turn up or down 1,000 revs either way...1/4 turn for 500 revs.....Revs increase 500-100 when on a hot run...hence being able to turn it down when idling....Not so sure on YB9 clocks...am assuming Bimota clocks with electronic pick up on the rev meter/tacho....if so...notoriously unreliable and lucky that it works at all..."if it isn't TOO broken...don't fix it"...we adapt the phrase for Bimotas....Yu can obviously tell what the engine speed is so go by ear instead...most of us are used to tachos not working on Bimotas...

Check with Paolo re filler cap....seal is not great...the rubber seal beneath perishes and shrinks.....replacements can only be bought by x100 unless Paolo has any....My Db1 has same filler cap...and that has one hand cut from a sheet of rubber...smear Vaseline/grease on the bottom face of the rubber ring...not too much...don't want it in your petrol tank....

hello, everybody,
I bought a NOS fuel cap, flap (€€€€!) from Bimota spares Paolo and it cured not only the esthetics but also the sealing of the rubber gasket. two problems solved with one golden stone. I'm happy.
I've also removed, dismanteld and cleaned the FCR flatside carbs. I've tried to synchronise them and I think I did an OK job as the engine idles more steadilly than before. I found however that the idle mixture screws idealy are set at about 3/4 turn from fully home indicating that the idle jets might be too large. I have shimmed the front disks as after 33K Km's they rattled somewhat... I fitted wave shims and it seems a tighter package alltogether but the prove of the pudding... I also replaced the 2005 Dunlop 208's for Michelin PP3's. I hope to have the first testride in about 4 days when the front wheel will be back from the tyre fitters.
Any tips on the best brake pads for these cast iron disks?

Just returned from a 600mile trip through the south of Brittan. The Yb, not realy suited to the poor UK pavement with its firm suspension and racer seating position behaved rather well. Two things I need to work on are the fuel consumption. It is way too rich at anything below 4 grand. And I keep rubbing and moving the rubber grommet covering the rear brake light switch on the master cilinder with the heel of my boot. It realy needs a piece of aluminium or carbon between my boot and the brake master. Did Bimota provided any or wil I have to make one myself?
Cheers,
William

Rear brake master cylinder...Bimota did make a carbon cover that acted as a heel guard, covering the master cylinder...but that was many years ago....The DB4 and Vdue both came with an alloy cover that should fit...as it fits over the 2 bolts that attach the master cylinder to the footpeg hanger